Design of a Human Hand Prosthesis

1 Design of a Human Hand Prosthesis A Major Qualifying Project Report submitted to the Faculty of the Worcester Polytechnic Institute in partial fulfillment of the requirements for the Degree of Bachelor of Arts Submitted by: Paul Ventimiglia (LA&E). Advised by: Professor Taskin Padir Professor Jerome Schaufeld Advisor Code: TP1. Project Code: RPAD. April 26, 2012. Abstract Current prosthetic hands have limited functionality and are cost prohibitive. A Design of a cost effective anthropomorphic prosthetic hand was created. The novel Design incorporates five individually actuated fingers in addition to powered thumb roll articulation, which is unseen in commercial products.

2 Fingertip grip force is displayed via LEDs for feedback control. The hand contains a battery and micro-controller. Multiple options for signal input and control algorithms are presented. A prototype will serve as a platform for future programming efforts. 1. Contents Abstract .. 1. Table of Figures .. 3. Table of Tables .. 4. Design of a Human Hand Prosthesis .. 5. 6. 1. Introduction .. 7. 2. Background information .. 8. Prosthetic hooks .. 9. Current prosthetic hands .. 12. Design methodology .. 16. Design requirements .. 17. 3. Mechanical Design .. 19. Finger Linkage Design .. 19.

3 Finger Joint/Drivetrain 20. Motor Selection .. 26. Compound Thumb 28. Hand Chassis 33. Cosmetic Covers and Grip .. 34. 4. Control considerations .. 37. Electronic Speed Controller 37. Microcontroller Selection .. 38. Fingertip Force Sensing .. 40. Grip Mode Selections .. 42. User Control 49. 5. Manufacturing Considerations and Functional Prototype .. 51. Bill of Materials .. 51. 6. Commercialization Considerations .. 55. As A Prosthesis .. 55. As a Research Platform .. 56. 7. Conclusion .. 57. Future Recommendations .. 57. 2. Works Cited .. 58. 60. Table of Figures Figure 1 Civil War Prosthetic Hook (Cowan, 2012).

4 7. Figure 2 Johns Hopkins APL Arm (New Launches, 2010) .. 8. Figure 3 DEKA Luke Arm (DEKA Research, 2009) .. 9. Figure 4 Hosmer 5x Prosthetic Hook (Amputee Supplies, Inc., 2010) .. 9. Figure 5 Prosthetic Hook and Harness (Prosthetics, 2010) .. 10. Figure 6 Body Powered Harness Motion (Schweitzer, 2011) .. 10. Figure 7 Sean Mchugh (Mchugh, 2012) .. 11. Figure 8 VASI Hand Family (Technologies, Liberating, 2012).. 12. Figure 9 Mech hands (Technologies, Liberating, 2012) .. 12. Figure 10 BeBionic Hand (Advanced Arm Dynamics, 2012) .. 13. Figure 11 iLimb Hand (Arthur Finnieston Prosthetics + Orthotics, 2012).

5 13. Figure 12 Darin Sargent (Sargent, 2012) .. 14. Figure 13 Michelangelo Hand (Schweitzer, 2011) .. 16. Figure 14 Initial Finger 4-Bar Motion Study .. 19. Figure 15 Initial Finger 2-Stage Reduction Design .. 22. Figure 16 Early Refined Finger 22. Figure 17 Final Finger Gearbox Section View .. 23. Figure 18 Final Finger Gearbox Solution .. 23. Figure 19 Finger Gearbox Assembly Exploded View .. 24. Figure 20 Finger Gearbox Assembly Exploded View 2 .. 25. Figure 21 Pololu 250:1 Gear Motor HP (Pololu, 2012) .. 27. Figure 22 Preliminary Design Demonstrating the Pinch Grip .. 28. Figure 23 Preliminary Design Demonstrating the Power 29.

6 Figure 24 Final Compound Thumb Gearbox Solution .. 30. Figure 25 Final Compound Thumb Gearbox Solution 2 .. 31. Figure 26 Labeled Thumb Assembly Exploded View .. 32. Figure 27 Main Hand Components Attached to Chassis Plate .. 33. Figure 28 Hand Cosmetic Covers Highlighted .. 34. Figure 29 Final Palm Cover Inside View .. 35. Figure 30 Final Back of Hand Cover Inside View .. 35. Figure 31 Fingertech TinyESC (Fingertech Robotics, 2012) .. 38. Figure 32 Arduino Pro Mini (Sparkfun Electronics, 2012).. 39. Figure 33 Analog Current Sensor on Breakout Board (Sparkfun Electronics, 2012).. 41.

7 Figure 34 Force Sensitive Resistor (Sparkfun Electronics, 2012) .. 42. Figure 35 Pinch Grip 1 .. 43. 3. Figure 36 Pinch Grip 2 .. 43. Figure 37 Power Grip Closed Fist 1 .. 44. Figure 38 Power Grip Closed Fist 2 .. 44. Figure 39 Key Grip 1 .. 45. Figure 40 Key Grip 2 .. 45. Figure 41 Ball Grasp 1 .. 46. Figure 42 Ball Grasp 2 .. 46. Figure 43 Open Palm Grasp 1 .. 47. Figure 44 Open Palm Grasp 2 .. 47. Figure 45 Index Point Mode .. 48. Figure 46 Myoelectric Control Example (Phillipe, 2012) .. 50. Figure 47 MQP Poster .. 60. Figure 48 Finger Assembly 61. Figure 49 Prototype Finger Assembly Side View.

8 62. Figure 50 Motor With Input Shaft and Worm .. 62. Figure 51 Lithium Polymer Battery for Prototype .. 63. Figure 52 Aluminum 1/2-20 Stud Turnbuckle Awaiting Modification .. 63. Figure 53 Laser Cut Motor Mounts and Potentiometer 64. Figure 54 Laser Cut Delrin Chassis Plate Standing In for Carbon Fiber .. 64. Figure 55 7075 Aluminum Final Gearbox Shafts .. 65. Figure 56 Potentiometer Glued to Delrin Potentiometer Mount with Soldered Wires .. 65. Figure 57 Finger Prototype Assembly 1 .. 66. Figure 58 Silicone Grip Attached to Finger .. 66. Figure 59 Finger Prototype Assembly Vertical.

9 67. Figure 60 Thumb Compound Gearbox Housings .. 68. Figure 61 7075 Aluminum Finger 4-Bar Linkages .. 68. Figure 62 Final Polycarbonate Finger Parts Next to Earlier Finger Parts .. 69. Figure 63 Final Base Link of Finger .. 69. Figure 64 Finger Prototype Assembly Upside Down .. 70. Figure 65 Final Finger Next to Human Finger Flexed .. 71. Figure 66 Finger Next to Human Finger Partially Extended .. 72. Figure 67 Assembled Finger With Parts in Background .. 73. Figure 68 Finger Assembly with Motor .. 74. Table of Tables Table 1 Motor Specifications .. 27. Table 2 Electronic Speed Controller Specifications.

10 37. Table 3 BOM for 1 Complete Finger Assembly .. 52. Table 4 BOM for 1 Complete Thumb Assembly .. 53. Table 5 BOM for Miscellaneous Hand Components .. 54. 4. Design of a Human Hand Prosthesis 5. Acknowledgments I would like to first and foremost thank my two advisors, Taskn Padir and Jerome Schaufeld for willing to work with me throughout the entire MQP process. I always enjoyed meeting with them and learning from their years of experience. I am especially glad they were willing to put up with me and my difficulties. I would also like to thank Matthew Simpson for helping me work in the machine shops and produce parts for the functional prototype.